1. Field of the Invention
This invention relates generally to the synchronization of a live picture with a recorded picture and, more particularly, is directed to the synchronization of a live picture with a recorded picture by generating a signal for controlling vertical synchronization of a video camera which views the live picture.
2. Description of the Prior Art
In many instances, for example, in television commercials and the like, it is desirable to successively view a first object followed by a second object having an identical configuration but with a different design thereon, so that only a change in the design is perceived by the viewer. As an example, it may be desirable to illustrate to a viewer ten different designs that are available on coffee cups. This can be accomplished by successively portraying each cup for approximately one or two seconds.
In order to focus the viewer's attention only on the change in design, when filming each cup, it is desirable that the cups be placed at the same position. In other words, if the cups are not exactly at the same position, during successive views of different cups, in addition to the design changing, the viewer will also perceive a shifting of each cup. Previously, it has been known to position the cups merely by sight or markings. It is to be appreciated that such positioning is inaccurate, and the viewer thereby still preceives the cups as shifting.
As another example, it may be desirable to provide a film clip in which an item appears out of thin air at a predetermined position. For example, after a person snaps his or her fingers, it may be desirable to place an object in the snapped fingers so that the viewer perceives the item appearing out of thin air into the fingers of that person. In this same regard, it is desirable to provide that the snapped fingers are in the same position before and after the item is placed therein so that no shifting is provided. However, as with the aforementioned "by sight" method, inaccuracies result and there is a shifting of the snapped fingers.
In order to overcome such problems, it has been proposed to utilize a video camera with the film camera. With such arrangement, the video camera produces a first composite video signal corresponding to a first object A, for example, a cup having a first design thereon, and supplies the first video signal to a storage device where it is recorded on, for example, a magnetic record medium. It is to be appreciated that the video camera is supplied with reference vertical and horizontal synchronizing signals from a synchronizing signal generator and, in response thereto, generates its own vertical and horizontal synchronizing signals as part of the first composite video signal in response to the leading edges of the referemce vertical and horizontal synchronizing signals supplied thereto. Because of delays in the video camera in generating the vertical and horizontal synchronizing signals, the latter signals generated by the video camera are delayed from the reference vertical and horizontal synchronizing signals supplied thereto from the synchronizing signal generator. The first composite video signal from the video camera corresponding to the first object A, which includes the vertical and horizontal synchronizing signals generated by the camera, is supplied to a storage device to be recorded on a magnetic record medium. Thereafter, object A, for example, a cup with a first design thereon, is replaced by an object B having a second design thereon. In order to make the objects coincident, object B is viewed by the video camera which, in turn, produces a second composite video signal which, along with the stored first composite video signal, is supplied to a monitor through a special effects generator. The two objects can then simultaneously be viewed on the monitor and object B can be moved accordingly.
Because of phase differences that may exist, the synchronizing signal generator which applies the vertical and horizontal synchronizing signals to the video camera is also supplied with the first composite video signal from the storage device and generates the reference vertical and horizontal synchronizing signals in phase alignment with the vertical and horizontal synchronizing signals of the first composite video signal from the storage device. However, because the video camera generates its own vertical and horizontal synchronizing signals which are delayed from the vertical and horizontal synchronizing signals from the synchronizing signal generator, the vertical and horizontal synchronizing signals for the second composite video signal corresponding to object B are delayed from the vertical and horizontal synchronizing signals of the first composite video signal corresponding to object A. As a result, even if object A and object B are perfectly coincident, when viewed on the monitor there will be an offset because of such delay. Therefore it becomes difficult, if not impossible, to provide coincidence between object A and object B.
Because the delay of the generated horizontal synchronizing signal by the video camera is of a relatively short duration, that is, a fraction of a horizontal scanning period, such delay can be compensated for by a delay circuit, for example, a delay circuit incorporated into the synchronizing signal generator. However, as to the delay of the vertical synchronizing signal generated by the video camera, it is to be appreciated that such delay may have a duration of a few horizontal scanning periods. However, to compensate for such delay, the vertical synchronizing signal from the synchronizing signal generator must be phase delayed for approximately one field interval less, of course, the few horizontal scanning periods of delay caused by the video camera. However, to delay the vertical synchronizing signal from the synchronizing signal generator by approximately one field interval is extremely complicated and expensive, if practically possible at all.